A singing synthesis system capable of artificially generating a singing voice like a human's can readily synthesize various sorts of singing voices and control singing representation with high reproducibility. Such systems have become an important tool for expanding a possibility of producing music accompanied by singing. Since 2007, a rapidly increasing number of end users have enjoyed producing music using commercially available singing synthesis software. Increased use of the commercially available singing synthesis software is of public concern, and such singing synthesis systems have become a hot topic for discussion over various media.
Singing synthesis technologies include manual adjustment of numeric parameters by a user with a mouse as described in non-patent document 1, voice morphing based on singing voices of the same lyrics sung by two singers as described in non-patent document 2, and emotional morphing applied to a plurality of singing songs sung by the same singer with emotional changes as described in non-patent document 3. Speech synthesis technologies include voice conversion between different speakers as described in non-patent documents 4 and 5, and emotional voice synthesis as described in non-documents 6 and 7. Most of emotional voice synthesis techniques deal with speech rhythm and speed, but some of them are focused on the use of voice conversion in accompaniment with emotional changes as shown in non-patent documents to 13. Further, there have been some studies on speech morphing such as a study on average voice generation from a plurality of voices as described in non-patent document 14 and a study on voice morphing close to a user's voice by estimating a ratio of a plurality of voices as described in non-patent document 15.
In contrast therewith, the inventors of the present invention proposed “a system for estimating singing synthesis parameter data” in JP2010-9034A (patent document 1) which is a system capable of receiving a user's singing voice as an input and adjusting synthesis parameters of existing singing synthesis software so as to mimic the pitch and dynamics of the input singing voice. The inventors developed a singing synthesis system named “VocaListner” (a trademark) as an implementation of the proposed system. Refer to non-patent documents 16 and 17.